The present invention refers to a pipe switch or multiport valve for pneumatically conveyed bulk material, and in particular to a pipe switch including a housing provided with a first port, a second part extending in axial direction of the first port and a third port having an axis extending at an angle of less than 90.degree. relative to the axis of the second port, and with the housing accommodating a cock for selectively connecting the first port with the second port and the third port in dependence on the position thereof and being rotatably supported in side cover plates of the housing via a shaft which extends perpendicularly to the plane containing the axis of the ports.
A pipe switch of this type is known and is actuatable manually, electromotively or electropneumatically for selectively feeding bulk material between a feeding area and a first and second receiving area or for selectively feeding bulk material from a first or second feeding area to a common receiving area. Basically, such a pipe switch can be pressure-operated or suction-operated. The housing and the cock are cast parts usually made of aluminum or chrome nickel steel. The inner wall of the housing is provided with grooves surrounding the entrance area of the respective ports and accommodating seals which ensure a sealing of the interior of the housing against a prevailing overpressure or underpressure during operation and cooperate with a respective circumferential area of the cock for sealingly closing the port which is not in use. From time to time, it is necessary to dismantle such pipe switches for cleaning purposes or inspection and maintenance. In view of frequently exposed assembly locations, a dismantling of the cast cock has proven to be difficult and dangerous because of its large weight when pipe switches of great nominal width are concerned.
A further drawback of a pipe switch of this type resides in the fact that the cock should be made of hardenable special cast when utilizing the pipe switch for highly abrasive bulk material e.g. granulates of plastic material with glass fiber filling. The use of such special cast is not only expensive but considerably restricts the material selection. For such cases, it was therefore proposed to use a pipe switch of a next higher nominal width with e.g. a cock of cast aluminum and including flow channels which accommodate bushings of correspondingly wear-resistant special alloys. Since the respectively used materials for the bushings and the cock can normally not be welded together, the bushings are mounted or attached by screwing or gluing. This, however, is rather cumbersome and still results in loose bushings or in insufficient sealing and, moreover, considerably increases the weight of the pipe switch.